Great Lakes Dead Zone

Meghan Fischofer & Emily Dubois

Great Lakes Dead Zone

Meghan Fischofer & Emily Dubois

What is a Dead Zone?

A dead zone is a term for hypoxia which is reduced level of oxygen in the water. While these hypoxic dead zones can occur naturally, most are created or enhanced by human activity, mainly excess nutrient from farms, untreated sewage and toxic factory waste. This increase in nutrients (mainly phosphate and nitrogen) in the water stimulates an overgrowth of algae. When all the algae dies, it sinks and decomposes in the water. The decomposition process of the algae dying all at once takes up the oxygen in the water and depletes the oxygen supply available for the healthy marine life. When this happens, it is referred to as a dead zone because most marine life either suffocates and dies from a lack of oxygen or fish and other mobile animals leave to find a more sustainable habitat. Waters that would once be filled with aquatic life turn into a “biological desert” (NOAA).

Figure 1: Eutrophication Process (Ocean Health Index)

Organisms Involved

While many are working towards the recovery of Lake Erie and the toxic dead zone it is becoming, some of the organisms inhabiting the lake are preventing the problem from being resolved. Zebra and quagga mussels along with round gobies were originally invasive species who were accidently brought to the Great Lakes on the backs of boats from river deltas around Europe's Black and Caspian Seas. While these mussels where not around in 1960 when Lake Erie faced a major dead zone, they have proven to be important factors in the return of the increase in algae and the growth of the lake's dead zone. They hurt the lake in many ways. First off, these mussels are very efficient feeders and consume algae so thoroughly that the water becomes clear. But this clear water only adds to the problem as the clear water helps sunlight penetrate the water more easier, simulating even more algae growth. Zebra and quagga mussels also only feed on "good algae" and not the toxic blue green algae that is causing most of the lake's problems. This in turn gives mycrocystic, a type of blue green algae, an advantage as its competitors are being removed. Lastly, the mussels excrete phosphorus in a form algae can easily consume, only increasing the amount of excess nutrients in Lake Erie's waters. OnEarth magazine says that "you could hardly design a more deadly toxic-algae-creating machine" (National Resources Defense Council).

Figure 2: Impacts of Dead Zone (PBS Newshour)

Ecological and Enviornmental Impacts

The dead zone that is taking over Lake Erie's waters has devastating impacts on organisms habiting the lake, the environment, and the ecology of a once healthy, thriving habitat. In 1969, when Lake Erie was facing a major dead zone Time magazine wrote "each day, Detroit, Cleveland and 120 other municipalities fill Erie with 1.5 billion gallons of inadequately treated wastes, including nitrates and phosphates. These chemicals act as fertilizer for growths of algae that suck oxygen from the lower depths and rise to the surface as odoriferous green scum." The chemicals from those fertilizers and other toxins literally turned Lake Erie to a green color with a rotten egg smell from the absence of oxygen. Lake Erie is the most fertile out of all the Great Lakes. While it contains only 2% of their waters, it inhabits 50% of their fish. Losing a lake this significant to organism populations would be devastating. One example of an organism in trouble is the Yellow Perch, a popular sport and commercial fish. Driven from their normal habitat of Lake Erie's cold, bottom layers, the perch is forced to inhabit Erie's surface waters where temperatures are too warm, their preferred prey is not available and they are more vulnerable to predators. The Yellow Perch is just one example of the hundreds of fish and other organisms effected by the loss of oxygen and unstable environment of Lake Erie during a dead zone (National Resources Defense Council).

Geographic Impacts

Lake Erie is the most heavily impacted of the great lakes, it is the fourth largest of the five lakes. Scientists have found the dead zones of the lake to be unexpectedly variable. Dead zones seem to disappear and reappear in different locations of the lake. Internal waves in the lakes cause these shifts in the dead zones (USGS). Communities all around the lake are affected by these dead zones as are families linked to jobs on the lake.

Figure 3: Map of Great Lakes (Newsbusters)

Economic Impacts

Lake Erie is an vital ecosystem for millions of people. 11 million people rely on Lake Erie as a source for their drinking water and 1.5 million jobs are linked to the great lakes. Changes in this fresh water ecosystem could wreak havoc on more than just the wildlife. Communities surrounding the lake as well as those who depend on the lake for their income will be heavily impacted. Lake Erie is one of the world largest commercial fisheries and recreational fishing alone is worth $7 billion annually. Populations of fish and other wildlife are being impacted and their habitats are shifting based on dead zones. These high nutrient levels, depletion of oxygen, and sporadic dead zones are altering food chains and negatively affecting the fishing and recreation industries around the lakes. (National Wildlife Federation).

Figure 4: Sources of Nutrients (World Resources Institute)

Restoration and Nutrient Management

A main source of the nutrients that cause eutrophication in the lakes is agriculture. Increased use of fertilizers as well as high levels of rainfall have caused the nutrient levels in the lake to rise. The best way to address the problem, is to fix it from the source. Some of the big name companies are employing more sustainable farming methods. New laws and policies need to be put in place to make substantial change as employing more sustainable methods can affect the food industry and can keep companies from wanting to change their practices (Nat Geo). The federal government has created a five-year plan known as the Great Lakes Restoration Initiative (GLRI). $475 million are invested in the first year alone on restoration and protection programs. These programs are funding education, beach cleanup, wildlife habitat restoration, and many more projects. There is an estimated $2 of economic benefit for every $1 invested in restoration (National Wildlife Federation).